If Modern Humans Came from Africa, What Explains the Loss

If modern humans came from Africa, what explains the loss of pigmentation seen in different races?

A) Levels of sunlight vary across the globe, so darker pigmentation wasn't needed in all areas of the world.
B) The lighter-pigmented humans are found in colder climates, where having less pigmentation is an advantage because it preserves heat.
C) The diet found in the areas where lighter-pigmented humans are found contains compounds that interfere with the production of pigmentation.
D) Lighter pigment allows for more efficient production of vitamin D, an advantage in areas with less sunlight.
E) None of the answer options is correct.